A Swedish study has cast doubt on the assertion that magnetic blankets aid blood flood and ease muscular tension in healthy horses.

Researchers from the University of Agricultural Sciences in Uppsala and the Department of Medical Engineering at Linköping University said static magnetic blankets were often claimed to induce increases in blood flow, reduce muscle tension and tenderness, and be beneficial in both prevention and treatment of musculoskeletal injuries in horses.

However, there were no studies that confirmed alleged beneficial effects of magnets on muscles of the back in healthy horses, Anna Edner and her colleagues said.

Edner and her fellow researchers, whose findings are to be published in the Equine Veterinary Journal, set about examining the effectiveness of the blankets in a prospective, randomised, blinded, placebo-controlled cross-over study.

Measurements of the back of 10 healthy horses were performed, assessing blood flow by photoplethysmography, skin temperature by use of thermistors in conjunction with digital infrared thermography, and mechanical nociceptive thresholds (MNTs) by algometry, which can be used to quantify muscle pain.

The horses’ behaviour was filmed during the procedure and scored on an ethogram.

Measurements were taken repeatedly for a 30-minute baseline period.

Thereafter a blanket with active, 900-gauss static magnets or placebo magnets was placed on each horse and measurements were performed for a 60-minute treatment period and a 30-minute post-treatment period.

The study procedure was repeated on the next day, when each horse received the alternative treatment.

Blood flow in muscle, skin temperatures, MNTs and behavioural traits did not differ between active and placebo magnetic blankets, the researchers found.

Skin temperature increased similarly during both active and the placebo blanket treatment.